Breathing assistance apparatus

ABSTRACT

The present invention provides a breathing assistance apparatus that has a convenient and effective method of cleaning internal conduits inside the apparatus. The breathing assistance apparatus is preferably a gases supply and humidification device. The cleaning method is a method of disinfection that is automated so minimal training is required to disinfect in particular an internal elbow conduit within the device. It is therefore not necessary to dismantle the gases supply and humidification device, therefore, inadvertent damage to the internal parts of the device is avoided. The present invention also provides a method of disinfecting a heated breathing conduit and a patient interface.

This application is a continuation-in-part of PCT/NZ2006/000330,entitled “Breathing Assistance Apparatus” which has an internationalfiling date of Dec. 15, 2006, which was published in English on Jun. 21,2007 under International Publication Number WO 2007/069922 which claimspriority of New Zealand Patent No. 544169, filed on Dec. 15, 2005 all ofwhich are hereby incorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a gases supply and gases humidificationapparatus that can be disinfected and reused for different patients. Theinvention also relates to a method for disinfecting apparatus parts thatextend the life of these parts for use by a single patient.

2. Summary of the Prior Art

A number of methods are known in the art for assisting a patient'sbreathing. Continuous Positive Airway Pressure (CPAP) involves theadministration of air under pressure to a patient, usually by a nasalmask. It is used in the treatment of snoring and Obstructive SleepApnoea (OSA), a condition characterised by repetitive collapse of theupper airway during inspiration. Positive pressure splints the upperairway open, preventing its collapse. Treatment of OSA with nasal CPAPhas proven to be both effective and safe, but CPAP is difficult to useand the majority of patients experience significant side effects,particularly in the early stages of treatment.

CPAP is also commonly used for patients with a variety of respiratoryillnesses, including Chronic Obstructive Pulmonary Disease (COPD).

Upper airway symptoms adversely affect treatment with CPAP. Mucosaldrying is uncomfortable and may awaken patients during the night.Rebound nasal congestion commonly occurs during the following day,simulating a viral infection. If untreated, upper airway symptomsadversely affect rates of CPAP use.

Increases in nasal resistance may affect the level of CPAP treatmentdelivered to the pharynx, and reduce the effectiveness of treatment. Anindividual pressure is determined for each patient using CPAP and thispressure is set at the patient interface. Changes in nasal resistanceaffect pressure delivered to the pharynx and if the changes are ofsufficient magnitude there may be recurrence of snoring or airwaycollapse or reduce the level of pressure applied to the lungs. Suchsymptoms can also occur in a hospital environment where a patient is ona respirator. Typically in such situations the patient is intubated.Therefore the throat tissue may become irritated and inflamed causingboth distress to the patient and possible further respiratory problems.

A number of methods may be employed to treat such upper airway symptoms,including pharmacological agents to reduce nasal disease, or heating thebedroom. One most commonly employed method is humidification of theinspired air using an in line humidifier. Two types of humidifier arecurrently used. Cold pass-over humidifiers rely on humidifying the airthrough exposure to a large surface area of water. While they are cheap,the humidity output is low at high flows, typically 2 to 4 mg/L absolutehumidity at flows above 25 L/min. The output is insufficient to preventmucosal drying. Heated water bath humidifiers are more efficient, andproduce high levels of humidity even at high flow rates. They areeffective at preventing upper airway mucosal drying, prevent increasesin nasal resistance, and are the most reliable means of treating upperairway symptoms. Oxygen is the most common drug prescribed tohospitalized patients. The delivery of oxygen via nasal cannula orfacemask is of benefit to a patient complaining of breathlessness. Byincreasing the fraction of inspired oxygen, oxygen therapy reduces theeffort to breathe and can correct resulting hypoxia (a low level ofoxygen in the tissues).

The duration of the therapy depends on the underlying illness. Forexample, postoperative patients may only receive oxygen while recoveringfrom surgery while patients with COPD require oxygen 16 to 18 hours perday.

Currently greater than 16 million adults are afflicted with COPD, anumbrella term that describes a group of lung diseases characterized byirreversible airflow limitation that is associated mainly with emphysemaand chronic bronchitis, most commonly caused by smoking over severaldecades. When airway limitation is moderately advanced, it manifests asperpetual breathlessness, without physical exertion. Situations such asa tracheobronchial infection, heart failure and also environmentalexposure can incite an exacerbation of COPD that requireshospitalization until the acute breathlessness is under control. Duringan acute exacerbation of COPD, the patient experiences an increase indifficulty of breathing (dyspnea), hypoxia, and increase in sputumvolume and purulence and increased coughing.

Oxygen therapy provides enormous benefit to patients with an acuteexacerbation of COPD who are hypoxic, by decreasing the risk of vitalorgan failure and reducing dyspnea. The major complication associatedwith oxygen therapy is hypercapnia (an elevation in blood carbon dioxidelevels) and subsequent respiratory failure. Therefore, the dose ofoxygen administered can be critical and must be precisely known.

To accurately control the oxygen dose given to a patient, theoxygen-enriched gas must exceed the patient's peak inspiratory flow toprevent the entrainment of room air and dilution of the oxygen. Toachieve this, flows of greater than 20 L/min are common. Such flows ofdry gases cause dehydration and inflammation of the nasal passages andairways if delivered by nasal cannula. To avoid this occurrence, aheated humidifier is used.

The majority of systems that are used for oxygen therapy or merelydelivery of gases to a patient consists of a gases supply, a humidifierand conduit. Interfaces include facemasks, oral mouthpieces,tracheostomy inlets and nasal cannula, the latter having the advantageof being more comfortable and acceptable than a facemask.

A group of patients who would benefit from humidification therapy arepatients who have mucociliary clearance deficiencies. These patientsoften have purulent mucus and are susceptible to infections frompathogens.

Heated humidified air with an abundance of water particles is an idealmedium to harbour disease carrying pathogens. Consequently, considerabledesign expertise has been required to provide the market with activepass-over humidifiers that deliver water molecules, in gas phase only,so that it is not possible for disease pathogens to be carried in air tothe patient. Water that condenses on the inner surfaces of the breathingcircuit or conduit at the end of a treatment session may harbourpathogens that would be delivered to the patient next time they use thedevice. This is particularly the case with humidification therapieswhere patients are receiving body temperature fully saturated air.

In hospital environments or similar it is often not possible for gasessupply devices, such as devices that deliver CPAP and include ahumidifier, to be used by multiple patients. If devices were to be usedin this manner all parts, from the humidification chamber to andincluding the patient interface, must be disposed of or cleaned to ahigh standard of disinfection in between use by different patients.Often CPAP devices and humidifiers are provided in an integrated unit,such as the Sleepstyle™ 600 series CPAP device of Fisher & PaykelHealthcare Limited. This CPAP device is predominantly used for home useby an individual. This device has internal tubing from the outlet of thehumidification chamber that is difficult to disinfect. As these devicesare difficult to disinfect they are often not used in settings such ashospitals or clinics where multiple patients will use the device.

In the home use situation when oxygen therapy and CPAP devices are usedby a single patient the lifespan of the breathing tube and patientinterface is determined by the mechanical lifespan of the parts and thebuild up of microbial pathogens on the breathing gases path of theseparts. Often it is hard to lower microbial contamination on thebreathing gas surfaces of these parts.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide a breathingassistance apparatus which goes some way to overcoming theabovementioned disadvantages or which at least provides the public orindustry with a useful choice.

Accordingly in a first aspect the invention may broadly be said toconsist in a breathing assistance apparatus adapted to deliverhumidified gases to a patient comprising:

a housing including an atmospheric inlet adapted to allow gases to entersaid housing,

a gases supply within said housing,

a gases supply outlet port in said housing, said gases supply outletport in fluid connection with said gases supply and adapted to in usemake fluid connection with the inlet of a humidifier of the type thatincludes both an inlet and an outlet, in order to supply gases to saidhumidifier via said inlet,

a patient return in said housing, adapted to make fluid connection withsaid humidifier outlet in use in order to receive humidified gases fromsaid humidifier in use,

a patient outlet on said housing, in use in fluid connection with saidpatient return and also in fluid connection or adapted to make fluidconnection with a breathing conduit for delivery of humidified gases toa patient,

a first disinfection conduit including a heating element, said firstdisinfection conduit adapted for connection between said gases supplyoutlet port and said patient outlet,

a controller in said housing adapted to supply power to the heatingelements of conduits connected to said breathing assistance apparatus,said controller adapted to supply power to said first disinfectionconduit when said first disinfection conduit is connected between saidgases supply outlet port and said patient outlet so as to heat the flowof gases through said first disinfection conduit to keep said flow ofgases at a predetermined temperature over a set period of time, saidcontroller simultaneously supplying power to said gases supply so as toprovide a flow of gases through said first disinfection conduit.

Preferably said breathing assistance apparatus further includes atemperature sensor located at or close to said patient return, saidtemperature sensor adapted to sense the temperature of gases flowingbetween said patient return and said patient outlet in use.

Preferably said controller is adapted to receive temperature data fromsaid temperature sensor, said controller supplying power to saiddisinfection conduit so that temperatures between said patient returnand said patient outlet reach a level of between 60° C. and 90° C. for atime period of approximately 20 minutes.

Preferably said controller provides a flow of gases through saiddisinfection conduit at a flow rate of approximately 10 liters perminute.

Preferably said breathing assistance apparatus further includes a seconddisinfection conduit adapted for connection between said patient returnand a point at or close to said atmospheric inlet, said controllersupplying power to said second disinfection conduit when said seconddisinfection conduit is connected between said patient return and saidpoint at or close to said atmospheric inlet so as to heat the flow ofgases through said second disinfection conduit to keep said flow ofgases at a predetermined temperature over a set period of time, saidcontroller simultaneously supplying power to said gases supply so as toprovide a flow of gases through said second disinfection conduit, atleast part of said supply of gases from said second disinfection conduitentering said atmospheric inlet.

Preferably said controller is further adapted to count and log thenumber of disinfection cycles that have taken place.

Preferably said apparatus further includes a filter connectable to saidpatient return to filter gases exiting said patient return.

Preferably said filter includes a projection adapted to increase thegases velocity where said gases exit said patient return.

In a second aspect the invention may broadly be said to consist in amethod of disinfecting a breathing assistance apparatus of the type thathas both an atmospheric inlet, a gases supply outlet port, a separatepatient outlet and a patient return, and which includes a gases supplycapable of supplying a flow of gases at a predetermined pressure fromsaid gases supply outlet port, and which also includes a controller tosupply power to the heating elements of conduits connected to saidbreathing assistance apparatus, said method comprising the steps of:

connecting a first heated gases disinfection conduit between said gasessupply outlet port and said patient outlet, said heated gasesdisinfection conduit of the type that includes a heating element,

providing a predetermined circulating flow of gases to said heated gasesdisinfection conduit from said gases outlet for a predetermined periodof time,

heating said heating element up to a predetermined temperature to heatthe gases passing through said heated gases disinfection conduit.

Preferably said predetermined period of time is between 20 and 40minutes.

Preferably said predetermined temperature is between 60 and 90 degreesCelsius.

Preferably said predetermined circulating flow is between 5 and 20liters per minute.

Preferably said method further includes the step of connecting a seconddisinfecting conduit between said patient return and a point at or closeto said atmospheric inlet.

Preferably said predetermined period of time is between 20 and 40minutes.

Preferably said predetermined temperature is between 60 and 90 degreesCelsius.

Preferably said predetermined circulating flow is between 5 and 20liters per minute.

In a third aspect the invention may broadly be said to consist in amethod of disinfecting at least one of a breathing conduit and patientinterface, said breathing conduit being connected to a breathingassistance apparatus of the type that includes a gases supply capable ofsupplying a flow of gases at a predetermined pressure or flow to apatient via said breathing conduit, and which is also capable ofproviding power to said breathing conduit, said breathing assistanceapparatus including a humidifying chamber and a heater capable ofheating said chamber and said breathing conduit including a heatingelement, said breathing assistance apparatus further including acontroller adapted to supply power to said heater and said heatingelement, said method comprising the steps of:

removing said water from said chamber and replacing said chamber on saidapparatus,

providing a predetermined flow of gases from said gases supply to saidchamber and at least one of said breathing conduit and patient interfaceover a predetermined period of time,

powering said heater and said heating element to heat said gasessupplied to said at least one of said breathing conduit and patientinterface to a predetermined temperature to dry and disinfect said atleast one of said breathing conduit and patient interface so as toprevent accumulation of bacteria in said at least one of said breathingconduit and patient interface.

Preferably said predetermined period of time is between 70 and 90minutes.

Preferably said predetermined temperature is between 40° C. and 75° C.

Preferably said patient interface is connected to said conduit, so thatgases supplied to said conduit also pass through said interface to dryand disinfect said patient interface.

Preferably said patient interface is not connected to said conduit, andsaid method includes the step of placing a cap on the patient end ofsaid breathing conduit before said heated gases are caused to flow insaid breathing conduit.

Preferably said method also includes the step of partly filling saidchamber with a disinfecting agent and replacing said partly filledchamber on said breathing assistance apparatus before providing apredetermined flow of gases and powering said heater.

Preferably said method includes the step of housing said patientinterface in a receptacle.

To those skilled in the art to which the invention relates, many changesin construction and widely differing embodiments and applications of theinvention will suggest themselves without departing from the scope ofthe invention as defined in the appended claims. The disclosures and thedescriptions herein are purely illustrative and are not intended to bein any sense limiting.

In this specification where reference has been made to patentspecifications, other external documents, or other sources ofinformation, this is generally for the purpose of providing a contextfor discussing the features of the invention. Unless specifically statedotherwise, reference to such external documents is not to be construedas an admission that such documents, or such sources of information, inany jurisdiction, are prior art, or form part of the common generalknowledge in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred form of the present invention will now be described withreference to the accompanying drawings.

FIG. 1 is an illustration of a breathing assistance apparatus that formsa breathing circuit in use, the breathing assistance apparatus includinga blower unit, a humidifier chamber, a delivery conduit and a patientinterface, the blower unit including a heater plate for heating thecontents of the humidifier chamber, the breathing assistance apparatussuitable for utilising the methods of disinfection of the presentinvention.

FIG. 2 is an exploded view of an elbow connection conduit of thebreathing assistance apparatus of FIG. 1, the elbow connection conduithaving a patient return end and a patient outlet end.

FIG. 3 is a perspective front view of the blower unit and humidifierchamber of FIG. 1 or FIG. 2, showing the humidifier chamber in place onthe blower unit.

FIG. 4 is a perspective front view of the blower unit of FIGS. 1 to 3,with the chamber removed, and showing a filter over the patient returnof the blower unit.

FIG. 5 is a front view of the blower unit of FIG. 4 showing detail ofthe patient return and a temperature sensor which is located within thepatient return

FIG. 6 is a perspective front view of the blower unit of FIG. 3 with thehumidifier chamber removed, and a first disinfection conduit which formspart of the apparatus of the present invention connected to the blowerunit, FIG. 5 also showing the filter over the patient return.

FIG. 7 is a close up cutaway view of the filter which is fitted over thepatient return, with detail of the filter cover and a projection thatextends within the patient return shown.

FIG. 8 is a schematic view of the connections between a controller whichis enclosed within the blower unit, and elements of the breathingcircuit such as the heater plate and the temperature sensor.

FIG. 9 shows the apparatus of FIG. 6, with a second disinfection conduitshown with one end connected to the patient return, and the body of thesecond disinfection conduit shown passing around the back of theapparatus to connect to an atmospheric inlet.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides a breathing assistance apparatus that canbe cleaned and sterilised easily and effectively. The present inventionalso provides a convenient and effective method for cleaning theinternal structure of the internal structure of the apparatus, and theconduits and interfaces used to provide gases to a user or patient.

As shown in FIG. 1, in a preferred form of the invention, a flow ofgases is provided to a patient by a breathing circuit 100. In thepreferred form, the gases pass in sequence through the followingelements of the system 100: a gases supply generator or flow driver 4(such as a blower, fan or compressor), a humidification chamber 5, aheated delivery conduit or inspiratory conduit 3, and a patientinterface 2.

Gases are passed to the patient by way of the patient interface 2. Thepatient interface 2 used with the apparatus of the present invention maybe a full-face mask, nasal mask, nasal cannula, oral mouthpiece ortracheostomy connection, but the preferred embodiments as describedbelow, and the Figures, describe and show a nasal cannula.

The patient 1 as shown in FIG. 1 is receiving humidified and pressurisedgases through a nasal cannula 2. The cannula 2 is connected to the gasestransportation pathway or inspiratory conduit 3 that in turn isconnected to an integrated gases supply or blower 4 , which in thepreferred form includes a humidification chamber 5. In the preferredembodiment of the blower 4, the blower 4 is contained in one housingwith the humidification chamber 5 rigidly coupled or connected to thisin use. The humidification chamber 5 extends out from the housing 10 andis capable in use of being removed and replaced (by a slide on movement,such as that described in WO04024429 of Fisher & Paykel HealthcareLimited, the contents of which are incorporated by reference) by thepatient or other user. The blower 4 includes a gases supply outlet port11, as shown in FIG. 2, that feeds the inlet 26 of the humidificationchamber 5. The inner end of the gases supply outlet port 11 is internalto the casing or housing 10 of the blower unit 4. In use, thehumidification chamber 5 contains a volume of water 6. It must beappreciated that the embodiment described above in relation to theintegrated blower and humidifier merely illustrates one form of thehousing of the integrated gases supply and humidifying device. A modularsystem in which the blower unit and the humidifier unit are separateitems could also be used.

The inspiratory conduit 3 is connected to a patient outlet 8 on thecasing 10 of the blower unit 4. In the most preferred form of theinvention, inspiratory conduit 3 contains heater wires 7 that heat thewalls of the inspiratory conduit 3 to reduce condensation of humidifiedgases within the conduit 3 and the patient interface 2.

In the preferred form, the humidification chamber 5 is formed from aplastics material and has a highly heat conductive base (for example analuminium base). The blower unit includes a heater plate 25, with theheat conductive base of the humidifier unit in contact with the heaterplate 25 in use. The blower unit 4 is provided with an electroniccontroller 200 that in the preferred form comprises amicroprocessor-based controller 200 executing computer software commandsstored in an associated memory. The controller 200 is contained withinthe housing 10. The controller 200 receives input from sources such as adial (not shown) or other user controls such as controls 101, throughwhich a user 1 of the device 4 may, for example, set a predeterminedrequired value (preset value) of humidity or temperature of the gasessupplied to patient 1 by the breathing circuit 100.

The controller 200 may in some forms receive other inputs. For example,data from temperature sensors or similar at a point or points in thesystem 100. Using these input and the internal programming, thecontroller 200 determines when (or to what level) to energise heaterplate 25 to heat the water 6 within humidification chamber 5. As thevolume of water 6 within humidification chamber 5 is heated, watervapour begins to fill the volume of the chamber 5 above the surface ofthe water 6. As gases enter the chamber through inlet 26, pass throughthe vapour space above the water 6, and exit the chamber through chamberoutlet 15, they become heated and humidified. The flow of gases (forexample air) is provided from the blower unit 4. If the gases used areentirely sourced from atmosphere, the gases enter the device 4 throughatmospheric inlet 9, which in the preferred form is located on the backof the device 4. It should be noted that at least a portion of the gasesprovided to a user by the system 100 could be oxygen, sourced from e.g.a wall-mounted port on a hospital wall or similar. This is useful if theuser 1 is undergoing oxygen therapy and requires gases that include atleast a fraction of oxygen.

The blower unit 4 preferably includes an internal variable speed pump orfan that draws air or other gases through the blower inlet 9. The speedof variable speed pump or fan is preferably controlled by the controller200, the speed of the fan varying in response to commands received bythe controller 200, the controller 200 varying these commands inrelation to inputs entered into the device 4 by the user, and in themost preferred form, from data received from sensors located in thesystem 100. The fan provides a gases flow throughout the system. Thepower drawn by the fan can be used by the controller 200 to calculatethe flow rate through the system, the controller 200 using a look-uptable, simple calculation algorithm, or similar to find the flow ratethat corresponds to a particular rate of power draw.

Disinfection of the Elements of the System

A partially exploded view of the blower unit 4 and humidificationchamber 5 is shown in FIG. 2. The blower unit 4 of the preferredembodiment includes an elbowed connection conduit or elbow conduit 12.One end of the elbowed elbow conduit 12 forms patient outlet end 8, towhich one end of the conduit 3 is connected in use. The other end formsa patient return 13, which is a gases return from the humidifier chamber5 to the housing 10 of the blower unit 4. The elbow conduit 12 isadapted so that in use chamber outlet 15 connected with the patientreturn 13 so that the elbow conduit 12 receives humidified gases fromthe humidification chamber 5. The humidified gases are then directedfrom the patient outlet 8 into the breathing conduit 3 for delivery topatient 1. It is preferred that the elbow conduit 12 is permanentlyfixed in place in the housing 4.

In some instances, there will be a requirement for multiple users to useat least the blower unit 4, as they will be used in hospitals, sleeplaboratories or leased by home care companies and hospitals for shortterm home users.

In order for the blower unit 4 to be safe for use on multiple patientsthe elbow conduit 12 must be disinfected to a high degree betweendifferent patients. For ease of use, it is preferred that the elbowconduit 12 is disinfected in situ. This ensures that even if the elbowconduit 12 can be removed, dismantling and potential damage to theinternal parts of the device 4 can be avoided. This is preferred, as itis often impractical to remove the elbow, as it may include electricalconnectors or similar, and therefore it is preferred that removal andreconnection as part of a cleaning process can be avoided. Furthermore,the high labour content and skill level required would make removing theelbow an unreliable cleaning method and may make the device moreunreliable.

Currently high level disinfection is performed either by thermal orchemical process. Thermal disinfection is normally carried out bysubmersion in hot water or steam and chemical disinfection by submersionin instrument grade disinfectants. These processes have disadvantagesfor high level disinfection of devices such as the blower unit 4 of thepresent invention as it cannot be submersed, steam sterilized, or easilychemically disinfected.

A first disinfection method allows for disinfection of the elbow conduit12, as described below. The breathing circuit 100 is provided with afirst disinfection conduit 14 to allow in particular for disinfection ofthe elbow conduit 12. The first disinfection conduit 14 is shown in FIG.3. In order to disinfect the elbow conduit 12, a first end 17 of thefirst disinfection conduit 14 is connected to the gases supply outletport 11 and a second end 18 to the patient outlet 8 of the elbow conduit12 (it should be noted that the humidifier chamber 5 has been removedfrom the blower unit 4 before the disinfection operation is carriedout). The disinfection conduit 14 includes a heating element 19 within,throughout or about the walls of the disinfection conduit 14, andincludes connectors at each end to allow connection with the gasessupply outlet port 11 and the patient outlet 8.

When the disinfection conduit 14 is connected between the gases supplyoutlet 11 and the patient outlet 8 as described above, the controller200 housed within the blower unit 4 is put into a cleaning mode. Drygases (e.g. air) are circulated through the disinfection conduit 14 andelbow conduit 12, entering the disinfection conduit 14 through the firstend 17 connected to the gases supply outlet port 11, and exiting throughthe second end 18 connected to the patient outlet 8 of the elbow conduit12, and venting to atmosphere. The circulated gases are heated by theheater 19 in the disinfection conduit 14. In the preferred embodiment,the gases are heated to a temperature of 80° C. However, a temperatureof between 60° C. and 90° C. is also considered to be suitable in somecircumstances.

The connectors at both ends 17, 18 of the disinfection conduit 14 arepreferably pneumatic connectors. At least the second end 18 of thedisinfection conduit 14 includes an electrical connector, adapted tomate with a connector on the casing 10, such that the heating element 19within the conduit 14 is supplied with power from the blower unit 4. Inother forms both ends 17, 18 may have both electrical and pneumaticconnections.

The controller 200 within the blower unit 4 that controls the heating ofthe heater plate 25 as described above, also controls the power to theheating element 19, to control the temperature conduit 14.

It is most preferred that the controller 200 of blower unit 4 includes auser setting that causes the blower unit 4 to provide a flow of gasesand simultaneously provide power to the heating element 19. The flow ofgases would for example be set at a level between 1 and 50 liters perminute. The power provided to the heating element 19 is such that thegases passing through the conduit 14 increase in temperature to 80° C.The controller 200 maintains the power to the heating element 19 tomaintain a predetermined temperature inside the elbow conduit 12 for aperiod of time, in order for the heated dry gases to disinfect the elbowconduit 12. It is preferred that the time is in the region of 20minutes.

Therefore in use, after a patient has used the breathing circuit 100,and before the next patient uses it, the patient, hospital staff or homecare supplier can connect the disinfection conduit 14 to the blower unit4 as described above, and use the controls to put the device into acleaning mode. As an example, a person might put the device into acleaning mode by pressing a button located on the casing 10, pressingthe button sending a signal to the controller 200 to activate a routinewhich causes the controller 200 to provide power to the heating element19 and the fan to run (so that gases are provided to the disinfectionconduit 14), with power provided to the heating element 19 so that it tokeep it at a predetermined temperature over a set period of time. Inthis first disinfection method or preferred method of disinfecting thedevice, it is preferred that the surface temperatures inside the elbowconduit 12 reach a minimum of 80° C. for a time period of 20 minutes,and the flow provided for circulation through the elbow conduit 12 isapproximately 10 liters per minute. However, other appropriatecirculating flows between 1 and 50 liters per minute and otherappropriate time periods and temperatures may be used.

In the most preferred form, a removable exhaust gases filter 20 isplaced on the patient return 13 of the elbow conduit 12 prior to thedisinfecting routine being run. This filter 20 is shown in more detailin FIGS. 5 and 6. In FIG. 5, a filter housing 21 is shown placed aboutthe patient return 13. The filter housing 21 is preferably made of aplastics material and can be simply removably attached to the patientreturn 13, and remains on the end of patient return 13 by a frictionfit. A circular piece of filter material (not shown in the figures) sitsinside the filter housing 21 and therefore occludes the patient return13, such that in use, gases exiting the patient return 13 are filteredbefore they exit to the ambient surroundings.

Referring to FIG. 6, the filter housing 21 is shown in further detail. Aprojection 22 is provided with the filter 20 and housing 21. Thistubular projection 22 sits within the patient return 13 and the filterhousing 21 sits about the projection 22 and over the end of the inlet13. The projection 22 has the purpose of increasing the gases velocityat the point where heated gases are exiting the patient return 13 (whenthe disinfection conduit 14 is in place as described above and in use).This has the effect of maximising the exhaust temperature of the exitinggases and minimising the temperature drop at the exit point. Thisensures there is a high level of disinfection throughout the entireelbow conduit 12. In use, the heated gases flow around the spherical end23 of the projection 22 down the sides of the tubular inlet end (in thedirection of arrows A) through apertures (not shown) in the projection22 through the filter material 20 and past the filter housing 21 intothe ambient surroundings.

In the preferred form of the present invention the elbow conduit 12 hasa temperature sensor 24 located within it, as shown in FIG. 7. Thissensor measures the temperature of gases travelling through the conduit12. In particular, in the preferred form, at the start of thedisinfection process, the controller 200 performs some checks to ensurethe disinfection conduit is correctly connected. Firstly, a check isperformed to determine that there is a heated gases flow through theelbow conduit 12 as follows. When the fan inside the blower unit 4starts to provide a flow of gas, and the heater element 19 of thedisinfection conduit 14 is turned on, the temperature of the heatedgases flow is measured by the temperature sensor 24. After apredetermined period the heater element 19 is turned off, with theblower unit 4 continuing to provide a flow of gases through thedisinfection conduit 14. After a preset or predetermined period of time,the temperature inside the elbow conduit 12 is again measured by thetemperature sensor 24. If the temperature has dropped between thesemeasurements, this indicates that there is a fluid connection of gasessupply connecting the flow source to the elbow conduit 12.

If a rise in temperature or a fall in temperature between measurementsis not detected by the sensor 24, the controller 200 causes an erroralarm to be indicated on the housing 10, or audibly relayed, or both,the alarm indicating that the disinfection conduit 14 is not connectedto the device 4 correctly.

In the most preferred form, the blower unit 4 also includes an ambientair temperature sensor (not shown) incorporated within it, and adaptedto measure the temperature of the surrounding atmospheric air. Thecontroller 200 therefore knows the fan speed (and therefore the flowrate), the ambient temperature (from the ambient temperature sensor),and the gases temperature inside the elbow connector 12 (fromtemperature sensor 24). Therefore, for any given time period over whichthe heating element 19 is powered, an expected temperature can becalculated by algorithms loaded into the controller 200, for the heatingand non-heating time periods described above. The expected temperatureas calculated can then be compared with the actual measured temperaturefrom the temperature sensor 24. If these match or are close to matching(within a tolerance range), then the checks are complete and indicatethat the disinfection conduit 14 and heating element 19 are connectedand working correctly. The first disinfection method or cleaning mode asdescribed above is then started.

In a variant of the first disinfection method discussed above, thedisinfection conduit 14 may be used on a blower unit 4 which does notinclude an internal temperature sensor inside the elbow conduit 12. Inthis variant a flow of gases at a predetermined rate is caused to passthrough the disinfection conduit 14, and a predetermined power level isapplied to the heating element 19 within the disinfection conduit 14.The ambient temperature is known from the ambient temperature sensor.The predetermined gases flow and predetermined power applied aredetermined in such a manner that the internal surface temperaturesinside the elbow conduit 12 will easily exceed the temperatures requiredfor high level disinfection for a range of ambient conditions. Thepredetermined temperature and power are preferably determined fromtesting and the like, and sub-routines are loaded into the controller200 which will ensure that the controller 200 provides power to the fanof the blower 4 and the disinfection conduit 14 of suitable levels.

The method of disinfection described above has been validated by anindependent laboratory, Toxikon Corporation of Bedford, Mass., USA.

The first method of disinfection as described above is automated sominimal training is required to disinfect the elbow conduit and it isnot necessary to dismantle the gases supply and humidification device.Therefore, inadvertent damage to the internal parts of the device isavoided.

Also, during the disinfection period the internal surface temperature ofthe elbow conduit is continuously monitored by the temperature sensor24, so each disinfection cycle can be validated and a ‘disinfectioncompleted’ symbol can be shown on the display at the completion of theprocess. Alternatively, if the disinfection cycle was not validated a‘failed disinfection’ symbol can be displayed to alert a user oroperator.

Disinfection of Inspiratory Conduit and Patient Interface

In a second form of the present invention a second disinfection method,or second method of disinfecting an inspiratory conduit 3 and patientinterface 2 is disclosed.

The inspiratory conduit 3 of the breathing circuit 100 preferablyincludes heater wires 7 within it. The wires 7 within the conduit 3 canmake it difficult or dangerous to clean and disinfect the conduit 3.Therefore, prolonged use of the conduit 3 by a patient 1 results in highmicrobial contamination inside the conduit 3. Consequently there is adanger of infection of the patient 1 from continual use of the conduit3. Therefore, for home use where patients 1 are reusing the inspiratoryconduit 3 and patient interface 2 over a substantial period it ispreferable to provide a method of cleaning and disinfecting the conduit3 and patient interface 2.

As shown in FIG. 1, one end of inspiratory conduit 3 is connected to thepatient outlet 8. The patient interface 2 is connected to the other endof the conduit 3.

In order to disinfect the conduit 3, or both of the conduit 3 and thepatient interface 2, dry heat is forced through the conduit 3 to heatand dry the conduit 3 such that bacteria and microbes are killed andcannot multiply. This is carried out when the patient 1 is not using thesystem 100. This is achieved as follows: After a patient 1 has completedtheir treatment (for example, each morning) the patient 1 removes thepatient interface 2 and then empties the humidification chamber 5,replacing the chamber 5 on the blower unit 4. The user or patient 1 thenactivates the second disinfection method, for example by pressing abutton on the housing 10 thereby activating a control sequence oralgorithm pre-loaded into the controller 200. Other mechanisms foractivating the sequence may be provided—for example, the device mayautomatically activate the conduit disinfecting control sequence after acertain predetermined time period has elapsed after completion oftreatment. Removal of the patient interface 2 triggers the start of thispredetermined time period.

Once the chamber 5 has been replaced on the heater plate 25, thecontroller 200 powers the plate 25 to maintain heat to the humidifyingchamber 5, and the blower unit 4 supplies gases through the chamber 5,via the gases supply outlet 11 and the patient outlet 8. it can be seenthat a supply of heated dry gases pass through the chamber 5 to theconduit 3. At the same time, the power to the heater wires 7 ismaintained to provide additional heat to the gases within the conduit 3.In the most preferred form, the gases are heated to approximately 40°C., but can be as high as 75° C. or more. The exit temperature from theconduit 3 is between 40° C. and 75° C. The disinfecting and heatingsequence preferably continues for between 30 and 120 minutes. In themost preferred form of the second disinfecting method, thehumidification chamber heater plate 25 heats the gases passing throughthe chamber 5 until the temperature of the gases in the patient return13 reaches 40° C. The heater wires 7 in the heated breathing conduit 3maintain the temperature of the gases passing through the conduit 3. Ifrequired, a third temperature sensor can be located at the patient endof the conduit to measure the temperature of the gases exiting theconduit 3 and the patient interface 2. This third temperature sensorwill indicate when the gases have reached a temperature of approximately50° C. In variations it is possible that this temperature may be raisedto as high as 70° C.

In other variations of this method, a cap is placed on the patient endof the heated breathing conduit 3 (in place of the patient interface 2).The cap allows the heated gases to build up in the conduit therebyincreasing the effectiveness of the disinfection process. Anotherpurpose of the cap is to ensure that patient 1 is not wearing thepatient interface 2. In the preferred form, the controller 200 ispre-loaded with flow and pressure characteristics for a range of users(to give maximum and minimum values of typical pressure and flow rateswhen the system 100 is being used by a patient 1). The pressure and flowcharacteristics when the cap is on the distal end of the conduit 3 willbe very different to the ‘in use’ characteristics when the patientinterface 2 is attached to the end of the conduit 3. If the pressure andflow characteristics are well outside the ‘in use’ parameters, this isindicative that the patient 1 is not wearing the interface 2 and that itis safe to heat the air in the heated breathing conduit to temperatureswell above safe gas breathing temperatures. This greatly improves theefficacy of the disinfection process.

In other variations, the patient interface 2 is left in place at thedistal end of the conduit 3 and is also exposed to the heated and drygases.

In further forms the patient interface 2 can be contained or housed in areceptacle while the second disinfection method is carried out. Thisallows increased heat build up to occur in the patient interface 2during the second disinfection process. Again, this increases theeffectiveness of disinfection. If the interface 2 is contained in areceptacle, it can be ensured that a patient 1 cannot be using theinterface 2 for breathing, and the controller 200 can detect there is nopatient connected, again because of the different pressure and flowcharacteristics. The heated breathing conduit 3 can then be heated totemperatures well above safe gases breathing temperatures. Again thisimproves the efficacy of the disinfection process.

The purpose of this disinfection process is to increase the useable lifeof the heated breathing conduit 3 by lowering microbial contamination onthe inside surfaces the gases pass over. If the heated breathing conduit3 is not cleaned regularly (this being difficult to achieve withconduits that include an internal heating wire 7), microbes can build toa level so that the inside of the surfaces of the conduit becomecolonised with bacteria. This lowers the useful life of the conduit 3,making treatment more inconvenient for the patient 1.

Tests were carried out on a heated breathing conduit in normal use for 2months at home by patients with no disinfection process. The conduitswere then tested for contamination. The results were that contaminationwithin the conduits had reached a level of bacterial contamination thatmade the conduits unsafe for use.

Further tests were also carried out with identical heated breathingconduits used under the same conditions for 2 months as described above.The conduits were then processed with the dry heat disinfection methoddescribed above. The result was that bacterial contamination was at alevel such that the conduits could continue to be used safely—the levelof contamination was lower compared to the conduits that had not beentreated.

This disinfection method by dry heat shows that bacterial contaminationcan be effectively lowered to a level that the conduits could continueto be used by patients.

For both the first and second disinfection methods outlined above, it ismost preferred that the controller 200 counts and logs the number ofdisinfection cycles that have taken place, storing these in memory sothat a user can access these via the display or by downloading these, orsimilar. The controller 200 will be able to recognise which of thedisinfection methods is taking place either by noting which cycle hasbeen selected by a user, or by comparing the flow and temperaturecharacteristics as measured, with pre-loaded parameters indicative of aparticular cycle. It is also preferred that the controller 200distinguishes between successful and failed disinfection cycles, loggingthese separately.

Disinfection of the Blower Unit

Another problem that has been noted with the use of breathing circuitssuch as the one described above is that of microbial build-up on theinterior parts (i.e. the internal gas path or gas passages from theatmospheric inlet 9, through the fan, to the gases supply outlet port11) of the blower unit 4. The disinfection method described above forthe preferred embodiment can be varied in the manner described below inorder to disinfect the internal gas path or gas passages of the blowerunit 4 or at least delay microbial build-up.

In this alternative (or third) disinfection method, a seconddisinfection conduit 114 is used as well as the first disinfectionconduit 14 described above. One end of the disinfection conduit 114 isconnected to the humidifier end of the patient return 13, to receive theheated gases passing out of the blower unit 4 when the firstdisinfection method outlined above is being carried out. The second endof conduit 114 is connected at or close to the atmospheric inlet 9. Inthe preferred form, atmospheric inlet 9 is adapted so that a pneumaticconnection can be formed between the second end of conduit 114 and theatmospheric inlet 9—for example by having the two elements mutuallyshaped to connect in this manner. It is preferred that this connectionis made in such a manner that the second end is not completely sealed toor around the atmospheric inlet 9—around 5% of the gases entering theatmospheric inlet 9 will be from atmosphere, with the remaining 95% ofthe gases entering the atmospheric inlet 9 being recirculating gasesfrom the conduit 114, the 5% air from atmosphere mixing with the 95% hotair from the conduit 114. The hot air then passes through the internalgas path of the blower unit 4, and dries and disinfects the internal gaspath in a similar manner as has been described above for the first andsecond disinfection methods. As for the first and second disinfectionmethods outlined above, the controller 200 logs the number of cyclesthat have occurred, distinguishing between successful and failed cycles.

Use of a Disinfection Agent to Assist Disinfection

The first, second and third disinfection methods outlined above usehearted dry air to disinfect, or at least reduce the incidence of,microbial build-up in elements of the breathing circuit 100. It has beenfound that using a disinfection agent in the gases state to assist thisprocess is beneficial and assists in the disinfection process. Thisshall be described in relation to the second disinfection methods whichhas been described above.

In this variant of the second method, the user removes and empties thechamber 5, as for the third disinfection method outlined above. However,the user then partly fills the chamber 5 with a disinfecting agent in aliquid state, and replaces the chamber 5 on the blower unit 4. Thechamber 5 is then heated by the plate 25. The contents of the chamber5—i.e. the disinfecting agent—is heated and begins to vaporise in asimilar manner to how the water 6 would vaporise if the system 100 wasin use. The vapour rises into the vapour space in the chamber 5 abovethe liquid disinfecting agent. A stream of gases is entering the chamberthrough inlet 26, and the vapour mixes with this stream of gases beforebeing carried out of the chamber 5 through the chamber outlet 15, alongthe patient return 13. If a conduit 3 (and possibly an interface 2) areconnected to the patient outlet 8, the vapour will pass along thisbefore exiting to atmosphere. As this vapour is a vapour form of adisinfecting agent, as it passes along the conduit 3 and interface 2, itwill assist in reducing the incidence of microbial or bacterialbuild-up. It is preferred when carrying out this method that the conduit3 only is disinfected in this manner, and that the cap is connected tothe end of the conduit to ensure that patient 1 is not wearing thepatient interface 2.

In the most preferred form, the disinfecting agent is a 3-6% solution ofhydrogen peroxide in water, or alternatively, a 2-4% solution offormaldehyde can be used. These are the most preferred concentration,although other concentrations can be used.

The invention claimed is:
 1. A breathing assistance apparatus adapted todeliver humidified gases to a patient, the breathing assistanceapparatus comprising a cleaning mode that is configured to supply aheated flow through a first disinfection conduit having a heatingelement, the breathing assistance apparatus comprising: a breathingassistance apparatus housing comprising an atmospheric inlet, apressurized gases supply within said breathing assistance apparatushousing and in fluid communication with said atmospheric inlet, a gasessupply outlet port in said breathing assistance apparatus housing, saidgases supply outlet port in fluid connection with said pressurized gasessupply, said gases supply outlet port sized and configured to makeremovable fluid connection with an inlet of a humidifier, a patientreturn in said breathing assistance apparatus housing, said patientreturn sized and configured to make removable fluid connection with ahumidifier outlet, a patient outlet on said breathing assistanceapparatus housing, said patient outlet in fluid connection with saidpatient return, said patient outlet sized and configured to makeremovable fluid connection with a breathing conduit, in a cleaning modewith a first end of the first disinfection conduit connected to thegases supply outlet port and a second end of the first disinfectionconduit connected to said patient outlet such that flow through thefirst disinfection conduit has not passed through said humidifier priorto flowing through the first disinfection conduit, a controller in saidbreathing assistance housing adapted to supply power to the heatingelement of the first disinfection conduit so as to heat the flow ofgases through the first disinfection conduit and said patient return tokeep said flow of gases above a predetermined temperature over a setperiod of time, a temperature sensor located at or close to said patientreturn, said temperature sensor adapted to sense the temperature ofgases flowing between said patient return and said patient outlet inuse, wherein said controller is adapted to receive temperature data fromsaid temperature sensor, said controller supplying power to saiddisinfection conduit so that temperatures between said patient returnand said patient outlet reach a level of between 60° C. and 90° C. for atime period of approximately 20 minutes and wherein said controllerprovides a flow of gases through said disinfection conduit at a flowrate of approximately 10 liters per minute, a second disinfectionconduit adapted for connection between said patient return and a pointat or close to said atmospheric inlet, said controller supplying powerto a heating element of said second disinfection conduit when saidsecond disinfection conduit is connected between said patient return andsaid point at or close to said atmospheric inlet so as to heat the flowof gases through said second disinfection conduit to keep said flow ofgases at a predetermined temperature over a set period of time, saidcontroller simultaneously supplying power to said pressurized gasessupply so as to provide a flow of gases through said second disinfectionconduit, at least part of said supply of gases from said seconddisinfection conduit entering said atmospheric inlet.
 2. A breathingassistance apparatus as claimed in claim 1 wherein said controller isfurther adapted to count and log the number of disinfection cycles thathave taken place.
 3. A breathing assistance apparatus according to claim1 wherein said apparatus further includes a filter connectable to saidpatient return to filter gases exiting said patient return.
 4. Abreathing assistance apparatus according to claim 3 wherein said filterincludes a projection adapted to increase the gases velocity where saidgases exit said patient return.
 5. A breathing assistance apparatusaccording to claim 1, wherein said controller supplies power to saidpressurized gases supply simultaneous with supplying power to saidheating element of the first disinfection conduit so as to provide aflow of dry heated gases through said first disinfection conduit.
 6. Abreathing assistance apparatus and disinfection unit combination, thebreathing assistance apparatus comprising a housing, a first flow pathdefined within the housing between an atmospheric inlet and a gasessupply outlet port, a second flow path defined within the housingbetween a gases return and a patient outlet, the gases supply outletport and the gases return configured for removable connection to ahumidification chamber; the breathing assistance apparatus comprising aflow driver along the first flow path, a controller controlling the flowdriver such that flow can be generated through the first flow path; andthe disinfection unit comprising a conduit, the conduit having a firstend connected to the gases supply outlet port such that flow from theflow driver does not enter the humidification chamber, the conduithaving a second end connected to the patient outlet such that flow fromthe flow driver enters the patient outlet without entering thehumidification chamber, the disinfection unit further comprising aheating element such that heat supplied for a cleaning mode originatesfrom the heating element of the conduit and heats a dry flow within theconduit created by the flow driver.
 7. The breathing assistanceapparatus and disinfection unit combination of claim 6, wherein thebreathing assistance apparatus comprises a humidification chamber thatis removably connected to the gases supply outlet port and the gasesreturn such that the humidification chamber must be removed from thegases supply outlet port before the disinfection unit can be connectedto the gases supply outlet port.
 8. The breathing assistance apparatusand disinfection unit combination of claim 6, wherein the breathingassistance apparatus comprises a breathing circuit that is removablyconnected to the patient outlet such that the breathing circuit must beremoved from the patient outlet before the disinfection unit can beconnected to the patient outlet.
 9. The breathing assistance apparatusand disinfection unit combination of claim 6, wherein the humidificationchamber forms a portion of a humidifier that is integrated into thehousing of the breathing assistance apparatus.
 10. The breathingassistance apparatus and disinfection unit combination of claim 6,wherein the gases return is defined at one end of a return passage andthe patient outlet is defined at another end of the return passage. 11.The breathing assistance apparatus and disinfection unit combination ofclaim 10, wherein the return passage is permanently fixed in placewithin the housing of the breathing assistance apparatus.
 12. Thebreathing assistance apparatus and disinfection unit combination ofclaim 10, wherein a temperature sensor is positioned along the returnpassage between the gases return and the patient outlet.
 13. Thebreathing assistance apparatus and disinfection unit combination ofclaim 6, wherein at least one of the first end and the second end of theconduit comprises an electrical connector.
 14. The breathing assistanceapparatus and disinfection unit combination of claim 13, wherein onlythe second end of the conduit comprises an electrical connector.
 15. Thebreathing assistance apparatus and disinfection unit combination ofclaim 13, wherein the controller controls the heating element of theconduit through the electrical connector.
 16. The breathing assistanceapparatus and disinfection unit combination of claim 15, wherein thecontroller controls the flow driver and the heating element such thatgas flow starts substantially simultaneously with power being providedto the heating element to generate heat.
 17. A breathing assistanceapparatus adapted to deliver humidified gases to a patient, thebreathing assistance apparatus comprising a cleaning mode that isconfigured to supply a heated flow through a first disinfection conduithaving a heating element, the breathing assistance apparatus comprising:a breathing assistance apparatus housing comprising an atmosphericinlet, a pressurized gases supply within said breathing assistanceapparatus housing and in fluid communication with said atmosphericinlet, a gases supply outlet port in said breathing assistance apparatushousing, said gases supply outlet port in fluid connection with saidpressurized gases supply, said gases supply outlet port sized andconfigured to make removable fluid connection with an inlet of ahumidifier, a patient return in said breathing assistance apparatushousing, said patient return sized and configured to make removablefluid connection with a humidifier outlet, a patient outlet on saidbreathing assistance apparatus housing, said patient outlet in fluidconnection with said patient return, said patient outlet sized andconfigured to make removable fluid connection with a breathing conduit,a controller in said breathing assistance housing, when in said cleaningmode, adapted to supply power to the heating element of the firstdisinfection conduit when the first disinfection conduit is connected tosaid breathing assistance apparatus between said gases supply outletport and said patient outlet such that flow through the firstdisinfection conduit has not passed through said humidifier prior toflowing through the first disinfection conduit so as to heat the flow ofgases through the first disinfection conduit and said patient return tokeep said flow of gases above a predetermined temperature over a setperiod of time, and a second disinfection conduit adapted for connectionbetween said patient return and a point at or close to said atmosphericinlet, said controller supplying power to a heating element of saidsecond disinfection conduit when said second disinfection conduit isconnected between said patient return and said point at or close to saidatmospheric inlet so as to heat the flow of gases through said seconddisinfection conduit to keep said flow of gases at a predeterminedtemperature over a set period of time, said controller simultaneouslysupplying power to said pressurized gases supply so as to provide a flowof gases through said second disinfection conduit, and at least part ofsaid supply of gases from said second disinfection conduit entering saidatmospheric inlet.
 18. A breathing assistance apparatus according toclaim 17 wherein said apparatus further includes a temperature sensorlocated at or close to said patient return, said temperature sensoradapted to sense the temperature of gases flowing between said patientreturn and said patient outlet in use.
 19. A breathing assistanceapparatus according to claim 18 wherein said controller is adapted toreceive temperature data from said temperature sensor, said controllersupplying power to said disinfection conduit so that temperaturesbetween said patient return and said patient outlet reach a level ofbetween 60° C. and 90° C. for a time period of approximately 20 minutes.20. A breathing assistance apparatus as claimed in claim 19 wherein saidcontroller provides a flow of gases through said disinfection conduit ata flow rate of approximately 10 liters per minute.
 21. A breathingassistance apparatus as claimed in claim 20 wherein said controller isfurther adapted to count and log the number of disinfection cycles thathave taken place.
 22. A breathing assistance apparatus according toclaim 17 wherein said apparatus further includes a filter connectable tosaid patient return to filter gases exiting said patient return.
 23. Abreathing assistance apparatus according to claim 22 wherein said filterincludes a projection adapted to increase the gases velocity where saidgases exit said patient return.
 24. A breathing assistance apparatusaccording to claim 17, wherein said controller supplies power to saidpressurized gases supply simultaneous with supplying power to saidheating element of the first disinfection conduit so as to provide aflow of dry heated gases through said first disinfection conduit.